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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS002 Oral Presentation 1756 Deposits of the tsunami of December 26, 2004, In Northern Indonesia: Simelue Island and the medan coast of Sumatra Island Dr. Razzhigaeva Nadya paleotsunami paleotsunami Larissa Ganzey, Tatiana Grebennikova, Elena Ivanova Sediments deposited during the tsunami of December 26, 2004, in coastal areas that differ in their structure and orientations relative to the tsunami front are studied with defining of the factors controlling particular features of the sedimentation under different wave intensities. The data obtained by the international expedition that studied the aftereffects of the tsunami in question from January- February, 2005. The sediments were studied along profiles orthogonal to the shoreline with available estimates of the tsunami run-up heights and distances. The lithology of tsunami-related deposits and data on various fossils (diatoms, foraminifers, and mollusks) are analyzed. The data obtained demonstrate that the sedimentation patterns during the tsunami were substantially variable in different coastal areas, which is explained by some other reasons in addition to the different wave transformation on the coasts with different configuration. A significant role in this process belongs to the geomorphologic structure and composition of the flooded zone and underwater coastal slope. Variably oriented coseismic motions is one of the factors influencing the sedimentation patterns. The most intense erosion occurred in the Northern part of Simelue Island , where the tsunami run ups exceeded 10 m. The thickness of the eroded layer amounts at least to 1.5 m. Coral reefs suffered the most intense erosion, particularly in the areas of coseismic uplifting and on the low shores subjected to a direct tsunami impact. The lithology of tsunami deposits depends on both the particular features of the tsunami and, largely, on the material sources. Under tsunami run ups up to 3-5 m high, when the erosion zone is limited by the upper part of the coastal slope, the beach, and adjacent old ramparts, the tsunami deposited well-sorted sands texturally similar to their counterparts from the beach and draining area. The textural characteristics of the sands are well sustained both vertically and horizontally. When the material from destroyed reefs is the main source for the tsunami deposits, they become more heterogeneous. Their most intense destruction occurred in the areas of coseismic uplifting. Here near the shoreline, the tsunami deposited moderately and poorly sorted sands, in the extended flooded zone, high tsunami run ups result in the sorting of this material, its grain size decrease, the disappearance of the coarse-grained fractions, and a unmodal grain-size distribution. The taxonomic composition of the microflora and fauna in the tsunami sediments shows that they mainly originate from the sediments of the erosion zone, coral reefs, and the upper part of the coastal slope. The paleotsunami deposits discovered are compared with their recent counterparts. Grants RFBR 05-05-64063, FEB RAS I № 06-I- ОНЗ-106. Keywords: tsunami, sediments

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS002 Oral Presentation 1757 Tsunami intensity as a quantification tool: the example of Mediterranean and Connected Seas Mrs. Anna Fokaefs IASPEI Eleni Daskalaki, Gerassimos A. Papadopoulos Quantification of tsunami waves is not an easy task given that adequate magnitude scales have not introduced so far. Alternatively, tsunami intensity is a tool that makes possible to describe semiquantitatively the effects of a tsunami wave in particular coastal sites. Traditional 6-grade tsunami intensity scales were introduced since 20s. A few years ago the so-called Papadopoulos-Imamura 12- grade scale was developed and applied in several tsunamigenic regions of the world. Mapping of a real intensity distribution as well as correlations between intensity and physical parameters of the wave (e.g. wave height, distance of penetration inland) can be performed. Therefore, the tsunami intensity is a potential tool for the post-event effect study, for the development of scenarios of expected effects from future tsunamis as well as for comparative studies. Such possibilities are shown with the example of the Mediterraneanand connected Seas. Intensities for hundreds of tsunami events have been estimated in both the classic 6-grade and 12-grade scales and correlations between the two scales are investigated. Intensities have been estimated for a long number of observation points of the large tsunami of 9 July 1956 in the South Aegean Seaand the intensity field has been mapped as a prototype example. Keywords: tsunami, intensity, scale

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